package local.sumw3.findmydevices.object.utils;

public class Base64 {

    private Base64() {
        super();
    }

    /**
     * Encode some data and return a String.
     */
    public final static String encode(byte[] d) {
        if (d == null)
            return null;
        byte data[] = new byte[d.length + 2];
        System.arraycopy(d, 0, data, 0, d.length);
        byte dest[] = new byte[(data.length / 3) * 4];

        // 3-byte to 4-byte conversion
        for (int sidx = 0, didx = 0; sidx < d.length; sidx += 3, didx += 4) {
            dest[didx] = (byte) ((data[sidx] >>> 2) & 077);
            dest[didx + 1] = (byte) ((data[sidx + 1] >>> 4) & 017 | (data[sidx] << 4) & 077);
            dest[didx + 2] = (byte) ((data[sidx + 2] >>> 6) & 003 | (data[sidx + 1] << 2) & 077);
            dest[didx + 3] = (byte) (data[sidx + 2] & 077);
        }

        // 0-63 to ascii printable conversion
        for (int idx = 0; idx < dest.length; idx++) {
            if (dest[idx] < 26)
                dest[idx] = (byte) (dest[idx] + 'A');
            else if (dest[idx] < 52)
                dest[idx] = (byte) (dest[idx] + 'a' - 26);
            else if (dest[idx] < 62)
                dest[idx] = (byte) (dest[idx] + '0' - 52);
            else if (dest[idx] < 63)
                dest[idx] = (byte) '+';
            else
                dest[idx] = (byte) '/';
        }

        // add padding
        for (int idx = dest.length - 1; idx > (d.length * 4) / 3; idx--) {
            dest[idx] = (byte) '=';
        }
        return new String(dest);
    }

    /**
     * Encode a String using Base64 using the default platform encoding
     **/
    public final static String encode(String s) {
        return encode(s.getBytes());
    }

    /**
     * Decode data and return bytes.
     */
    public final static byte[] decode(String str) {
        if (str == null)
            return null;
        byte data[] = str.getBytes();
        return decode(data);
    }

    /**
     * Decode data and return bytes. Assumes that the data passed in is ASCII
     * text.
     */
    public final static byte[] decode(byte[] data) {
        int tail = data.length;
        while (data[tail - 1] == '=')
            tail--;
        byte dest[] = new byte[tail - data.length / 4];

        // ascii printable to 0-63 conversion
        for (int idx = 0; idx < data.length; idx++) {
            if (data[idx] == '=')
                data[idx] = 0;
            else if (data[idx] == '/')
                data[idx] = 63;
            else if (data[idx] == '+')
                data[idx] = 62;
            else if (data[idx] >= '0' && data[idx] <= '9')
                data[idx] = (byte) (data[idx] - ('0' - 52));
            else if (data[idx] >= 'a' && data[idx] <= 'z')
                data[idx] = (byte) (data[idx] - ('a' - 26));
            else if (data[idx] >= 'A' && data[idx] <= 'Z')
                data[idx] = (byte) (data[idx] - 'A');
        }

        // 4-byte to 3-byte conversion
        int sidx, didx;
        for (sidx = 0, didx = 0; didx < dest.length - 2; sidx += 4, didx += 3) {
            dest[didx] = (byte) (((data[sidx] << 2) & 255) | ((data[sidx + 1] >>> 4) & 3));
            dest[didx + 1] = (byte) (((data[sidx + 1] << 4) & 255) | ((data[sidx + 2] >>> 2) & 017));
            dest[didx + 2] = (byte) (((data[sidx + 2] << 6) & 255) | (data[sidx + 3] & 077));
        }
        if (didx < dest.length) {
            dest[didx] = (byte) (((data[sidx] << 2) & 255) | ((data[sidx + 1] >>> 4) & 3));
        }
        if (++didx < dest.length) {
            dest[didx] = (byte) (((data[sidx + 1] << 4) & 255) | ((data[sidx + 2] >>> 2) & 017));
        }
        return dest;
    }

    /**
     * A simple test that encodes and decodes the first commandline argument.
     */
    public static final void main(String[] args) {
        if (args.length != 1) {
            System.out.println("Usage: Base64 string");
            System.exit(0);
        }
        try {
            String e = Base64.encode(args[0].getBytes());
            String d = new String(Base64.decode(e));
            System.out.println("Input   = '" + args[0] + "'");
            System.out.println("Encoded = '" + e + "'");
            System.out.println("Decoded = '" + d + "'");
        } catch (Exception x) {
            x.printStackTrace();
        }
    }
}